[bigiain]

Curiously, that sort of language is used by camera people. Aperture and shutter speed are not the same thing, but they are inextricably linked to each other (in a way that dynamic range (in the amplitude sense) and frequency response/range are not nearly so linked). In a "camera article", the phrase " ... its fast f/1.4 shutter speed." would probably be in the context of saying something about one or more of the sensor's size, sensitivity, or noise-floor.

http://en.wikipedia.org/wiki/Lens_speed

"Lens speed refers to the maximum aperture diameter, or minimum f-number, of a photographic lens. A lens with a larger maximum aperture (that is, a smaller minimum f-number) is called a "fast lens" because it delivers more light intensity (illuminance) to the focal plane, achieving the same exposure with a faster shutter speed."

[Stratoscope]

Sorry to disagree, but a knowledgeable camera person would never talk about a "fast f/1.4 shutter speed". A camera article, review, or blog post that said that would be loudly criticized in the comments.

The phrase just doesn't make sense - that's why I chose it as an analogy. It especially doesn't make sense as a figure of speech referring to some characteristic of the sensor.

A more sensitive and less noisy sensor may let you use a higher ISO setting and therefore allow either a faster shutter speed or a smaller aperture for the same overall exposure.

A lens with a wider aperture would allow you to use a faster shutter speed or a lower ISO with the same exposure.

Similarly, a slow shutter speed would allow you to use a smaller aperture for more depth of field, or a lower ISO setting for less noise. Or a fast shutter speed would allow you to a wider aperture to blur the background. Again all with the same overall exposure.

Aperture, shutter speed, and ISO setting are closely linked - changing any one of them will affect your overall exposure, or you can change two or all three of them in combination to get the same exposure while altering other characteristics like motion blur or depth of field.

But they are three very different things, and even in casual conversation someone who knows cameras would not mix them up.

BTW this goes way back to the film days. Shutter speed and aperture work the same now as they did then, the only difference is that you changed ISO rating by buying a new roll of film instead of turning a dial.

[hrjet]

I think you are missing a characteristic of lenses called the f-ratio, which is sometimes described as fast or slow. This is not specific to cameras; it is a general term used in optics. The f-ratio is the ratio of the aperture to the focal length. Even telescope lenses and mirrors are described similarly. For example, a telescope with an f/4 mirror can be described as a fast telescope.

Not only that, a lot of the terms have been misappropriated in camera lingo. The camera folks express aperture as an f-ratio, which is extremely confusing.

[Stratoscope]

Thank you, you are absolutely right! I should have said "f-ratio" everywhere I used "aperture".

I'll leave my previous comment in its incorrect state in the hope that people will see yours to correct and clarify it. :-)

> The camera folks express aperture as an f-ratio, which is extremely confusing.

Isn't it the other way around? I think the mistake we self-proclaimed "knowledgeable" camera folks make is using the term "aperture" where we really should say f-ratio.

For example, I have two Olympus Micro Four Thirds lenses that are both f/1.8: a 45mm and a 75mm. Looking at these lenses it's pretty obvious that the f/1.8 is an f-ratio: the front element of the 75mm is much wider than the 45mm, as you'd expect.

So thanks to your comment, I will endeavor to use "f-ratio" where I've been misusing "aperture".